Named for its chief Senate sponsor, Illinois Democratic Sen. Richard Durbin, the amendment capped the amount of money debit-card issuing banks could make from each debit transaction.

At the time the amendment was debated, supporters asserted the savings retailers saw from debit transactions could be passed on to consumers, but the EPC says its research demonstrates that gasoline retailers have not been doing that.

Drawing on numbers from the American Automobile Association, the Federal Reserve, the U.S. Energy Information Administration and others, the EPC estimated that gasoline retailers have kept roughly $1 billion in Durbin savings instead of passing it back to gasoline consumers.

“Whenever Congress meddles in an industry debate over who pays what, consumers never win,” says Trish Wexler, spokeswoman for the EPC. “One side gets a leg up and keeps their windfall, while consumers end up footing the bill.

“No one is surprised to see that gas retailers are keeping billions of dollars for themselves, while their customers continue to be punished at the pump,” Wexler said. “Americans should go to their gas stations and demand what’s theirs – a discount for debit.”